The present invention relates to a system for creating a fault diagnosis on production machines using a knowledge-based evaluation of signals representing the quality of the products produced, having a knowledge base containing the expert knowledge required for the evaluation, having software units intended for access to the said base, and having a user interface.
Systems of this type, which are referred to as expert systems, have been known for some time, in particular for the fault and defect diagnosis of electronic components; see in this respect, for example, the article "An Expert System for Help to Fault Diagnoses on VLSI Memories" by T. Viacroze et al in the Journal for the International Symposium for Testing and Failure Analysis (ISTFA), October/November 1988, Los Angeles, pp. 153-158. The system described in this article first of all analyses the data of the tester and then derives from the knowledge of the knowledge base the appropriate rules for the causes of the defects. Then, at a second stage, a further analysis takes place in dialog with the operator and, finally, a defect diagnosis takes place, which provides forward and backward adjustment.
Systems which are to be used efficiently for diagnosis in the case of complexly constructed machines must be capable of describing at least several hundred individual parts and their arrangement in subassemblies or subsystems, as well as of applying typically up to 100 or 200 rules. In addition, a good integration into a conventional and extensive program environment, which carries out the storage and preprocessing of the signals mentioned, must be ensured. In practice, moreover, a response time in the range of seconds, where possible even less, is expected. At present, such requirements can be met only by large systems, the use of which is out of the question for the typical user, for reasons of cost.
The invention has the object of designing a system of the type mentioned at the beginning in such a way that a rapid and reliable fault diagnosis is possible with an inexpensive computer. This requirement is significantly more important in the case of production machines than in the case of test systems for electronic circuits, since in the case of these machines every defect generally results in defective or deficient products and therefore has to be rectified in the shortest possible time.